Correlation of penicillin-induced lysis of Enterococcus faecium with saturation of essential penicillin-binding proteins and release of lipoteichoic acid.
Clinical isolates of Enterococcus faecium that had a range of susceptibilities to penicillin were found to differ significantly in their responses to the antibiotic. In the penicillin-susceptible group (MIC, less than or equal to 4 micrograms/ml), the cessation of growth (bacteriostasis) at 10 x the MIC of penicillin appeared to correlate with the inhibition of penicillin-binding protein (PBP) 5*, whereas the onset of lysis (bactericidal effect) at higher antibiotic concentrations (100 x the MIC) was concomitant with the inhibition of the lower-affinity PBP 5. In contrast, in the resistant (MIC, greater than or equal to 8 micrograms/ml) group (in which most of the strains did not contain PBP 5*), the degree of saturation of PBP 5 seemed to determine the physiological response to the antibiotic: low levels of saturation caused growth inhibition, whereas almost complete saturation correlated with lysis. The penicillin-induced cell lysis of both penicillin-susceptible and -resistant strains was attributed, at least in part, to the extensive loss of acylated lipoteichoic acid into the growth medium.
al-Obeid
S
S
Laboratoire de Microbiologie Médicale, Université Pierre et Marie Curie, France.
Gutmann
L
L
Williamson
R
R
D001426:Bacterial Proteins; D002352:Carrier Proteins / Q000032:analysis / Q000378:metabolism*; D004754:Enterobacter / Q000187:drug effects* / Q000378:metabolism; D006602:Hexosyltransferases; D008070:Lipopolysaccharides / Q000378:metabolism*; D008826:Microbial Sensitivity Tests; D002267:Muramoylpentapeptide Carboxypeptidase / Q000032:analysis / Q000378:metabolism*; D010403:Penicillin Resistance; D046915:Penicillin-Binding Proteins; D010406:Penicillins / Q000494:pharmacology*; D010458:Peptidyl Transferases; D010641:Phenotype; D013682:Teichoic Acids / Q000378:metabolism*
D001426:Bacterial Proteins; D002352:Carrier Proteins; D008070:Lipopolysaccharides; D046915:Penicillin-Binding Proteins; D010406:Penicillins; D013682:Teichoic Acids; C009900:lipoteichoic acid; D010458:Peptidyl Transferases; D006602:Hexosyltransferases; D002267:Muramoylpentapeptide Carboxypeptidase